Removing Entity Instances

Managed entity instances are removed by invoking the remove method,
or by a cascading remove operation invoked from related
entities that have the cascade=REMOVE or cascade=ALL elements
set in the relationship annotation. If the remove method
is invoked on a new entity, the remove operation is ignored,
although remove will cascade to related entities that have
the cascade element set to REMOVE or ALL in the relationship annotation. If remove is
invoked on a detached entity it will throw an IllegalArgumentException, or the transaction commit will fail. If remove is
invoked on an already removed entity, it will be ignored. The entity’s
data will be removed from the data store when the transaction is completed,
or as a result of the flush operation.